The present invention relates to devices for deploying body implantable prostheses intended for fixation in body cavities, and more particularly to devices that utilize guidewires in the delivery and placement of stents.
Stents are employed in a variety of patient treatment and diagnostic procedures, for fixation in blood vessels, biliary ducts and other body lumens to maintain the passages. For example, a radially self-expanding stent can be deployed in an artery following a percutaneous transluminal coronary angioplasty (PTCA) procedure or a percutaneous transluminal angioplasty (PTA) procedure. The stent resists a tendency in the vessel to close, thus countering acute reclosure and plaque restenosis. A highly preferred construction for a radially self-expanding stent, disclosed in U.S. Pat. No. 4,655,771 (Wallsten) is a flexible tubular braided structure formed of helically wound thread elements. Wallsten teaches use of a catheter for delivering the stent to the fixation site. A pair of grips maintain the stent at the distal end of the catheter, and are controlled by an operational member at the proximal end of the catheter, to release the stent after positioning and initial medial expansion of the stent.
Another prosthesis construction is disclosed in U.S. Pat. No. 4,681,110 (Wiktor). A flexible tubular liner, constructed of braided strands of a flexible plastic, is delivered into the aorta by a main catheter tube, with the prosthesis carried at the distal end of the main tube. A secondary tube, inside the main catheter tubing and terminating just proximally of the liner, is held in place as the main tube is withdrawn. Thus the liner is deployed initially at its distal end, and radially self-expands against an aneurism to direct blood flow past the aneurism.
Yet another approach to deploying self-expanding stents is shown in U.S. Pat. No. 4,732,152 (Wallsten et al). Often referred to as the xe2x80x9crolling membranexe2x80x9d method, this approach involves a tube or membrane folded over upon itself to provide a double wall for maintaining a self-expanding stent at the distal end of a catheter. The outer wall of the membrane is movable proximally to expose the stent and allow radial self-expansion, beginning at the distal end of the stent.
Prostheses also have been constructed of plastically deformable materials, where upon a dilatation balloon or other means is required to radially expand the stent, e.g.. as shown in U.S. Pat. No. 4,733,665 (Palmaz). In Palmaz, a radially expandable vascular graft is delivered by a delivery catheter, with the graft surrounding a dilatation balloon of a balloon catheter. For deployment, the balloon catheter is expanded, thus to expand the graft.
Regardless of the type of prosthesis, its deployment frequently involves guiding the catheter or other delivery appliance through convoluted paths defined by arteries or other body passages. A well known technique for guiding the delivery catheter includes initially positioning a guidewire along the desired path, with the distal end of the guidewire near the treatment site and a proximal portion of the guidewire remaining outside of the body. The delivery catheter is formed with a lumen that runs the length of the catheter. When the proximal end portion of the previously positioned guidewire is threaded into the distal end of the delivery catheter, the delivery catheter can be advanced distally over the guidewire, ultimately to the treatment site for stent deployment.
Procedures that employ guidewires often require exchanging of treatment appliances. For example, a balloon catheter may be employed in a PTA or PTCA procedure, followed by placement of a stent or other prosthesis. This exchange or replacement of catheters requires that the proximal portion of the guidewire protruding from the patient""s body be longer than the balloon catheter, the prosthesis delivery catheter, or any other catheter involved in the procedure. This creates difficulty in maneuvering the guidewire and catheters due to the catheter length dimensions involved, which can range from 30 to 300 centimeters. In addition to handling difficulties, the guidewire and catheter tubing generate a substantial frictional force, due to the length along which their respective exterior and interior surfaces interact.
Therefore, it is an object of the present invention to provide a device for delivering and deploying a body implantable prosthesis using a prepositioned guidewire that protrudes from the patient""s body a distance substantially less than heretofore required.
Another object is to provide a prosthesis delivery device capable of utilizing a prepositioned guidewire without the need for a guidewire lumen running the entire length of the device.
A further object is to provide a prosthesis deployment device including an outer catheter and a coaxial inner catheter movable axially within the lumen of the outer catheter, in which the inner catheter includes a guidewire receiving lumen only along its distal portion, with a proximal termination open to the exterior of the inner catheter and alignable with an opening through the outer catheter, thus to facilitate passage of the guidewire from the innermost lumen to the exterior of the outer catheter.
Yet another object is to provide a prosthesis delivery device as part of a system of several devices alternatively advanced over a previously positioned guidewire, with exchanges of the devices being substantially simplified due to a shorter guidewire and reduced guidewire/device friction.
To achieve these and other objects, there is provided an apparatus for deploying a prosthesis at a treatment site within a body lumen. The apparatus includes an elongate prosthesis carrier having a proximal end region and a distal end region including a prosthesis support segment. The carrier has a carrier wall, and a guidewire lumen running axially of the carrier at least along the prosthesis support segment. A first opening is formed at the distal end of the support segment for admitting a guidewire into the guidewire lumen. A second opening through the carrier wall at the proximal end of the support segment provides egress of the guidewire out of the guidewire lumen, whereby the carrier contains the guidewire only along the prosthesis support segment. A prosthesis retaining means releasibly supports a prosthesis in a delivery state along the support segment of the carrier. When in the delivery state, the prosthesis has a reduced radius along its axial length to facilitate delivery of the prosthesis to a treatment site in a body lumen. A control means, operably associated with the retaining means, causes the retaining means to release the prosthesis when the support segment is positioned near the treatment site, thus to facilitate deployment of the prosthesis in a radially expanded state at the treatment site.
One preferred retaining means is a flexible, elongate outer catheter having a catheter lumen for containing the carrier. The outer catheter and carrier are movable relative to each other toward and away from a delivery configuration in which the outer catheter surrounds and radially compresses the prosthesis. Withdrawal of the outer catheter, i.e., proximal movement relative to the carrier, frees the prosthesis for radial expansion. The outer catheter advantageously has a slit running axially from a point near the proximal end of the support segment when the catheter and carrier are in the delivery configuration, to a proximal end region of the outer catheter. This allows the portion of the guidewire proximal to the guidewire lumen to be alternatively positioned within or outside of the outer catheter, as desired.
As compared to a conventional delivery apparatus that receives a guidewire along its entire length, the device of the present invention is substantially easier to manipulate. The proximal or exchange portion of the guidewire that protrudes from a patient""s body need not be longer than the entire device, but merely longer than the distal end region. Consequently it is substantially easier for the physician to manipulate a properly positioned guidewire, and easier to position the prosthesis delivery device for advancement along the guidewire. Friction between the guidewire and device occurs only along the distal end region, rather than along the entire length of the device. Typically, the device has a total length up to twenty times the length of the distal end region alone. Thus, static and dynamic frictional forces are substantially reduced, facilitating advancement of the device to the treatment location, particularly over a tortuous path to the desired location.
A preferred carrier is an inner catheter having a distal tip and a radiopaque marker proximally of the distal tip wherein the guidewire lumen is open to the distal tip and extends to the second opening through the wall of the inner catheter. Preferably the second opening is aligned with the distal portion of the slit when the device is in the delivery configuration. A channel or groove can be formed in the inner catheter, beginning at the proximal end of the catheter lumen and extending to the proximal end region of the inner catheter, for containing the portion of the guidewire between the outer catheter and the inner catheter. More preferably, the groove is aligned with the slit along the outer catheter.
The inner catheter with its abbreviated guidewire lumen is advantageous in connection with stents, in a configuration where the stent surrounds the inner catheter, and is surrounded by either the outer catheter, a rolling membrane or the outer catheter in combination with a sleeve extended proximally from the distal tip. In each case, the member or members surround the stent and maintain the stent in its reduced radius state along the prosthesis support segment. In the case of a radially self-expanding stent, stent release is achieved by moving the outer catheter proximally with respect to the inner catheter to free the stent for radial self-expansion.
Conversely, in the case of a plastically expanded stent, it is advantageous to incorporate a dilatation balloon along the inner catheter, particularly along the prosthesis support region. The balloon, surrounded by the stent or other prosthesis, is expandable by a fluid under pressure, provided through a balloon inflation lumen running substantially the entire length of the inner catheter.
Thus in accordance with the present invention, treatment procedures involving deployment of prostheses by means of a previously positioned guidewire are substantially simplified. The physician and others involved in the procedure are freed from the need to accommodate undue lengths of the guidewire and the attendant difficulty in advancing the prosthesis delivery device, and can devote their attention directly to the procedure at hand. The device is readily adapted to deploy either elastically deformable or plastically deformable stents, and can employ a stent retaining sleeve or rolling membrane, or utilize a dilatation balloon to radially expand the stent.